Vacuum-assisted pad conditioning system and method utilizing an apertured conditioning disk

ABSTRACT

A method and apparatus for conditioning polishing pads that utilize an apertured conditioning disk for introducing operation-specific slurries, without the need for additional tooling, platens, and materials handling. The method and apparatus utilize a vacuum capability to pull waste material out of the conditioning pad and through the apertured conditioning disk to evacuate the apparatus through an outlet port, the apparatus may also include self-contained flushing means and a piezo-electric device for vibrating the pad conditioning apparatus.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 10/819,754, filedApr. 7, 2004 and allowed Apr. 19, 2007, which is a continuation-in-partof U.S. Pat. No. 7,052,371 issued May 30, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to the fields of semiconductorfabrication, microelectromechanical systems (MEMS) fabrication, andprecision polishing; and specifically to a method for the removal ofwaste products from the polishing process, and for the introduction ofmultiple, different slurries during Chemical Mechanical Polishing (CMP)and planarization.

2. Description of Related Art with Respect to Semiconductor Fabrication

An integrated circuit generally consists of a silicon wafer substratetypically produced or fabricated as a disc with a diameter of 100 to 300millimeters and a thickness of 16 to 40 mils. Metallic, dielectric andinsulator depositions forming interconnected circuits are created on awafer by a series of processes, such as lithography, vapor deposition,and oxidation, that produce the desired electrical circuitry. Anelectrical insulating layer, up to one-micron in thickness, is thendeposited over the electrical circuit layer. With each layer, amultiplicity of undesired irregularities occur on the surface. Theseirregularities are on the order of 0.05 to 0.5 microns. It is criticallyimportant that these irregularities be planarized, so that new layers ofcircuitry can be developed without loss of focus in lithography, wherebyaccurate interconnections can be formed between layers.

Various techniques have been developed and used to effect the removal ofthese irregularities. Chemical Mechanical Polishing (CMP) (planarity)has become a key technology to remove irregularities and achieverequired planarity, layer and line width geometries of microelectronicdevices. A CMP system generally consists of the following components: 1)a polishing pad mounted on a rotating or orbital platen or belt; 2) astream of polishing slurry (oxidizer and abrasive) whose chemistry andabrasive media is important to polishing performance; 3) large amountsof ultra pure water (UPW) used as a lubricant or flushing medium/agent;4) slurry components and flushing agents. Additionally, to adjustchemistry or fluid properties during processing; 5) a diamond endeffector which controls the surface condition and asperity profile ofthe polishing pad; and 6) the wafer to be polished mounted in a carrieron a rotating head which supplies the polishing pressure.

The introduction of slurry under the wafer, and the removal of wasteproducts from the polishing and conditioning process, are dependent onthe centrifugal force of the rotating pad, the action of the endeffector, and the flow of slurry plus UPW.

Irregularities on the wafer are removed with a slurry of oxidatingchemicals and very fine abrasive particles continually presented to itssurface. Polishing or planarity is generally accomplished with the waferplaced face down on the polishing pad that is rotating beneath the waferthat is itself rotating around a central axis. Linear and orbitalmethods are also utilized and this invention is applicable to thoseprocesses and tools.

Current polishing tools and processes consist of a single operation stepper platen because of operation with specific slurries. Additionaltools, platens, and materials handling are required to supportmulti-step polishing operations such as that required for copper CMP.

There currently exists no means of using different chemicals, andabrasives of different materials or particle sizes, without separateequipment or extensive changeover and/or manual cleaning of thepolishing equipment.

Polishing pads are generally made of a plastic (urethane) material. Theremoval rate of wafer irregularities is affected by the pressure appliedto the wafer against the polishing pad, the relative speed of the slurryon the wafer, the amount of fresh slurry presented to the surface of thepolishing pad, and the circuit pattern of the wafer. The introduction ofslurry under the wafer, and the removal of waste products from thepolishing process, are dependent on centrifugal force of the rotatingpad, the action of the end effector, and the flow of slurry andcomponents and UPW. This type of flushing does not always remove thewaste. Large settled abrasive particles from the slurry, andagglomerated slurry and wastes, form in the pored and grooves of thepad, and between diamond particles on the conditioners. Commercialapplications have large volumes of UPW used in production andsignificant amounts of wastewater that must be treated.

The rate of wafer polishing depends upon the pressure applied to thewafer, the slurry, and the diamond head on the end effector arm toroughen or condition the polishing pad, to provide a consistent asperityprofile. In cross-section, the pad has regions of peaks and valleyswhich both carry slurry and provide pressure to the abrasive particlestherein. The pad generally consists of a hard or soft urethane materialwith pores and/or fibers dispersed throughout the active layer. Thefibers and/or urethane give the pad rigidity, provide pressure to theabrasive/wafer interface, and aid in the removal of material from thesurface of the wafer. The pores act as a reservoir for the slurryfacilitating the chemical contact and interaction with the wafersurface. The chemical interaction is an important ‘accelerator’ over anabrasive-only polishing situation, and therefore is critical to overallprocess performance and control.

The diamond end effector generally consists of diamond particlesembedded in a metal matrix in the form of a rotating disk. The disk isprincipally used to texture the polishing pad so that a sustainable rateof planarization can occur on the wafer and wafer to wafer. It is alsoused to remove used slurry and debris from the pad. The used slurry anddebris often occurs as large hard agglomerations which consist ofsilicon dioxide (SiO₂), dielectric and metals that become embedded inthe polishing pad. These materials reduce removal or polishing rates andrepeatability, and can produce defects in the form of scratches thatdamage the wafer surface and device performance (opens, shorts). Datafrom the semiconductor industry reveal that 60% of chip loss is due tocontamination. The CMP process has been reported to be a major source ofthis contamination.

The uncontrolled delivery and removal (flushing) of process fluids canalso cause polishing waste to build-up on many surfaces within thetooling. When dislodged, these dried/agglomerated compounds can lead toadditional defects. Slurry has proven to be “unstable”, prone toagglomeration due to shear forces in delivery systems, heat, and ageeffects. There is also potential for diamond particles to fracture or betorn from the metal matrix of the end effector disk and scratch thewafer surface. Within typical polishing times, from 60 to 600 seconds,there is significant causal mechanisms for scratching and more controlof the process is required.

Presently this debris is removed from the pad with copious flushing ofthe pad with UPW and/or slurry. This method relies on centrifugal force,or other pad movement dynamics, on the liquid to carry off the waste andagglomerates. This is a very uncontrolled method of removal because theflushing cannot break-up the static layer of slurry on the pad surface,nor is it able to dislodge the slurry in the holes of the pad. Thiscould lead to additional agglomerates of slurry becoming deposited inholes and recesses of the pad. This slurry can become dislodged, at alater time, and damage subsequent wafers. The reliance of these“rotational forces” to present new slurry to the wafer/pad interface isalso less controlled or repeatable than required, causing variation inremoval rates and uniformity.

Polishing pad surfaces, which typically contain pores, holes or groovesfor channeling the slurry between the wafer and the pad, requireconditioning to create a consistent polishing interface. Slurry anddebris from the wafer must be removed by continually “abrading” or“conditioning” the pad surface. Additionally, oxidizing slurriessometimes used in this process contribute to the contamination of thepad by interacting with device layer metals forming harder oxidecompounds; or layer delaminations, causing potential contamination andscratching of the wafer.

One apparatus that attempts to solve the problems defined above isdescribed in U.S. Pat. No. 6,508,697, incorporated herein by reference,in which a system for conditioning rotatable polishing pads used toplanarize and polish surfaces of thin integrated circuits deposited onsemiconductor wafer substrates, microelectronic and optical systems, isdisclosed. The system is comprised of a pad conditioning apparatus,process fluids, and a vacuum capability to pull waste material out ofthe conditioning pad, self-contained flushing means, and a means forimparting a vibratory motion to the pad conditioning abrasive or fluids.The pad conditioning apparatus is comprised of an outer chamber in agenerally circular configuration with an inlet port for introducingprocess fluids and/or UPW and an outlet port for supplying negativepressure.

Considering the prior art conditioning apparatus described above, it isan object of the present invention to provide a method, using such asystem, for conditioning polishing pads with a self-contained cleansingmeans for removing debris and loose slurry, as it is dislodged duringthe conditioning process.

It is also an objective to provide means for the introduction ofdifferent (multi-step) operations with specific slurries or additiveswithout additional tools, platens, and materials handling.

Another objective is to allow for neutralization of slurry chemistrybetween steps.

A further objective is to allow for the introduction ofalternative/additional slurry or chemical feeds.

Yet another objective is to allow for multi-step polishing on eachplaten.

A still further objective is to increase through-put by allowing a moreaggressive first polishing step, and subsequent, finer abrasive/chemicalselectivity near the planarization endpoint.

Another objective is to eliminate intermediate material handling and toallow for single platen processing of copper and barrier metal films.

Yet another objective is to extend utility/life of single and doublehead polishing tools.

Yet another objective is to reduce defectivity through more selectiveendpoint control via slurry change (chemistry or abrasive).

Yet another objective is to improve uniformity by reducinghandling/alignment/fixture variations seen by wafer.

BRIEF SUMMARY OF THE INVENTION

The pad conditioning system used in the present invention, as set forthin U.S. Pat. 6,508,697 referred to above, utilizes abrasive disks thathave an open structure to collect debris or swarf as it is being abradedoff of the substrate surface. The system has a pad conditioningapparatus, process fluids, a vacuum self-contained flushing means, and apiezo-electric device for vibrating the pad conditioning abrasive. Thedebris, s it is being created, is pulled through the holes of theabrasive and magnetic support, into a chamber behind the support, andinto a conduit to a disposal system. Jets of water, other cleaning, orneutralizing chemicals are sprayed through the abrasive in conjunctionwith the waste removal. This flushing/abrading/vacuum cleaningthoroughly cleans the polishing pad surface, enabling alternativematerials to be introduced without cross contamination. All of theseelements combine in operation to provide a unique and effective systemfor conditioning and cleaning polishing pads. They also allow for theintroduction into the conditioning, cleaning and polishing processesoperation-specific slurries or other chemicals, without the need forextensive retooling, platen change-out, and additional materialhandling.

The pad conditioning apparatus has an outer chamber in a generallycircular configuration with an inlet port for introducing process fluidsand/or UPW, and an outlet port for attaching negative pressure. Theouter chamber houses a rotating impeller shaft. The shaft of theimpeller assembly protrudes through an opening in the top surface of theouter chamber and is attached to the equipment's end effector assembly.A support disk, a magnetic disk or mechanical fastening means, and anabrasive conditioning disk, are attached to the impeller in a stackedconfiguration. As described in U.S. Pat. No. 4,222,204, incorporatedherein by reference, the abrasive disk is held in place magnetically ormechanically, offering full support of the disk, because it pulls thedisk flat to the support disk. The assembly is constructed with alignedholes that allow debris on the polishing pad to be vacuumed up throughthese holes.

In operation, the outside chamber is held stationary with an attachedhose connected to a vacuum facility. The water or slurry is introducedeither from an inlet port on the outer chamber, or from the center ofthe impeller through a water collar.

A series of pressurized water holes radiating out from the center of theimpeller disk allows full coverage of the abrasive disk and aids in thebreak up of the static layers in the pores of the polishing pad. Thevacuum action pulls the water and debris immediately up through thealigned holes in the support, magnetic, and abrasive disks, and therotating impeller blades sweep the water and debris into the vacuumpickup outlet and into the disposal system. The aligned holes, or “openstructure”, in the stacked disks allows collection of debris or swarf,as it is being dislodged from the surface of the pad, allowingcontinuous conditioning and cleaning without interference of the debrisbetween the abrasive disk and the surface of the wafer, The magneticfastening structure allows for rapid changeover and provides controlledflatness for the abrasive. A mechanical method can also be used whichwould be gimbaled for alignment and cushioning. Vacuum pulls the wastesfrom the process, and lifts the polishing pad asperities into anuncompressed position. Select holes also introduce process fluids, suchas cleaning chemicals, slurry, passivating agents, complexing agents,surfactants, and UPW, and even cleaning gasses, to the pad in a muchmore controlled (pressure, location, sequence, and pad/wafer surfaceconditions, for instance) fashion.

A self-contained flushing system provides water to loosen and flush thedebris up the disks holes into the impeller chamber and on through tothe disposal system, A sealed bearing at the top of the outer chamberprevents water or process fluids from escaping. This flushing methodalso reduces the amount of UPW that is presently needed to flush thepolishing pad. This saves on costly slurry, the volume of UPW, and theexpensive waste disposal.

The impeller provides firm backing for the magnetic disk or mechanicalfastening and abrasive disk. The magnet is secured to the support diskmechanically or by an adhesive. The abrasive disk is either magneticallyor mechanically secured to the support disk. This system allows forperiodic cleaning of the pad conditioning apparatus, as well as periodicreplacement of the magnet and abrasive disks, without the need todisassemble the entire outer chamber and inner impeller assembly, whichwould incur extensive down time.

A piezoelectric transducer is provided near the free end of the endeffector arm or fluid stream. When excited with a high frequencyvoltage, transducer imparts a low amplitude vibration to the padconditioning apparatus, further enhancing the breakup and removal of thestatic layer of slurry on the polishing pad surface. A small verticalforce imparted by the end effector arm on the polishing pad also aids inbreaking up glazing of the slurry, and aids in dislodging particleswedged in the polishing pad surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 5 illustrate the prior art system of U.S. Pat. No.6,508,697.

FIG. 1 is a perspective view of the major elements of the ChemicalMechanical Polishing (CMP) system used in the present invention with thewafer holder removed.

FIG. 2 is a top schematic view of the constituent components used in thepresent invention.

FIG. 3 is a view of the outer chamber taken along line 6-6 of FIG. 2.

FIG. 4 is a section view of the conditioning apparatus used in thepresent invention taken along line 7-7 of FIG. 2.

FIG. 5 is an exploded view of the constituent components of theconditioning apparatus used in the present invention showing the outerchamber and impeller assembly.

FIG. 6 is a block diagram showing the method of the present invention.

FIG. 7 is an exploded view of an inventive impeller arrangement formedin accordance with the present invention.

FIG. 8 is a cut-away side view of the impeller arrangement of FIG. 7.

FIG. 9 is an isometric bottom view of the impeller arrangement of FIG.7.

FIG. 10 illustrates an alternative impeller assembly of the presentinvention, including at least one vacuum port in an impeller blade.

FIG. 11 illustrates an alternative impeller element configuration, usingcylindrical members instead of impeller blades.

FIG. 12 is a side view of the arrangement of FIG. 11

FIG. 13 illustrates an alternative arrangement of the cylindricalimpeller elements as shown in FIGS. 11 and 12.

FIG. 14 is a graph illustrating improved polishing pad removal rate whenusing the polishing pad conditioning system of the present invention.

FIG. 15 is a graph illustrating improved polishing slurry activity as afunction of the vacuum force applied during the conditioning process.

FIGS. 16(a) and (b) contain photographs of the pressure gradient acrossthe surface of an abrasive conditioning disk, FIG. 16(a) associated withthe prior art and FIG. 16(b) associated with an embodiment of thepresent invention.

FIG. 17 is a simplified top view of a CMP apparatus illustrating thelocation of an abrasive conditioning disk torque measuring apparatus,used in accordance with the present invention to determine physicalparameters of the polishing pad.

DETAILED DESCRIPTION

The present invention relates to a method of conditioning polishing padsused in Chemical Mechanical Polishing or Planarizing (CMP) Systems forremoving irregularities on semiconductor wafer substrates. The specificdetails of the preferred embodiment provide a thorough understanding ofthe invention; however, some CMP system elements which operate inconjunction with the present invention have not been elaborated onbecause they are well known and may tend to obscure other aspects thatare unique to this invention. It will be obvious to one skilled in theart that the present invention may be practiced without these othersystem elements.

Referring to FIG. 1, a perspective view of a typical CMP system 10 isillustrated generally comprising a polishing head (not shown) thatapplies pressure to wafer 11 against a polishing pad 12 through a wafercarrier and support arm (not shown), and a polishing pad conditioningapparatus 15. Wafer 11 is rotated on polishing pad 12 that is secured torotating, orbital or linear platen 13. (The wafer carrier, support armand motor are not shown). A stream of polishing slurry 14 generallycontaining an oxidizer, abrasive and/or ultra-pure water (UPW) is pouredon the polishing pad surface 12 a and in cooperation with the rotatingmotion of wafer 11 acts to remove a few tenths of microns of surfaceuneveness on the wafer 11 after each layer of integrated circuitfabrication. Pad conditioning apparatus 15 operates to restore andmaintain polishing pad surface 12 a as it is changed by the polishingaction. Motor 17, as seen in FIG. 2, pivots end effector arm 16 in anarc about fixed shaft 18 while simultaneously providing rotationalmotion and a downward force 40 to pad conditioning apparatus 15. Debrisfrom the polishing operation is removed through outlet 41.

A pad conditioning apparatus 15 used in the present invention is shownin the top view of FIG. 5 and is configured to mechanically andelectrically interface with end effector arm 16. Pad conditioningapparatus 15 is designed to automatically dispense chemicals, slurryand/or UPW, so as to condition polishing pad surface 12 a, and vacuumout debris formed by the polishing process, without interfering with thepolishing process or incurring excessive down time. Hose 21, which isattached to vacuum outlet port 22 on the periphery of conditioningholder 20, pulls debris into a vacuum facility (not shown). Hose 23,which is attached to inlet port 19, projects through the top center ofconditioning holder 20 and provides a stream of abrasive slurry forconsistent coverage of the pad surface 12 a, and/or providesneutralizers, UPW, or cleaning agents, for flushing and lubrication. Toenhance debris removal, piezo-electric device 24, when excited with ahigh frequency voltage through electrical connection 25, imparts a lowamplitude vibratory impulse to conditioning apparatus 15, therebyagitating debris particles on conditioning pad surface 12 a, causing thedebris particles to become dislodged for easier removal.

Outer chamber 30 of conditioning holder 20 shown in FIG. 3 is a viewtaken along line 6-6 of FIG. 2. Outer chamber 30 of the currentembodiment, is approximately four inches in diameter and three incheshigh. It will be obvious to one skilled in the art that the presentinvention may be practice with dimensional characteristics other thanthose described, up to and inclusive of the entire working surface ofthe pad.

FIG. 4 is a sectional view taken along line 7-7 of FIG. 2, and shows theimpeller assembly 32 with support disk 34, magnetic disk 35, andabrasive disk 36, attached to impeller blades 33. Holes 37 in each ofthe disks are aligned, such that debris is pulled from polishing disk 12to vacuum outlet 22. Process fluid is taken in through hose 23 andevenly distributed through outlets 38 in impeller disk 39, to polishingpad 12, through holes 37. Seal 31 between outer chamber 30 and impellershaft 19 prevents process fluid from escaping. An annular channel 40, inouter chamber 30, can provide a secondary means of introducing processand flushing fluids to polishing pad 12.

FIG. 5 is an exploded view that more clearly shows the constituent partsof conditioning apparatus 15 with screw attachment holes 41 securingsupport disk 34 to impeller blades 33. Although only four impellerblades 33 are shown in this view, other impeller blade configurations,including non-rotating “BAR”/chamber configurations, will provide thesame function as that described in this embodiment.

FIG. 7 illustrates, in an exploded view, an improved impellerarrangement 80 formed in accordance with the present invention. Asshown, impeller arrangement 80 comprises an outer chamber 82, animpeller assembly 84, a magnetic disk 86 and a conditioning disk 88. Itis to be understood that the use of a magnetic disk (or, in general, anytype of “support” for conditioning disk 88) is considered optional,where in the alternative a (thicker) conditioning disk 88 would becoupled to impeller assembly 84 without an intervening support member.Further, the use of an outer vacuum chamber 82 is considered as only oneexemplary embodiment of a vacuum supply system. Alternatives coupleddirectly to the impeller assembly without the need to encase the entirearrangement are possible and considered to fall within the spirit andscope of the present invention.

As with the arrangements described above, conditioning disk 88 includesa fine diamond grit for mechanically removing waste material from apolishing pad (not shown). An improvement associated with arrangement 80of the present invention is the use of an innovative impeller assembly84 for the application of one or more conditioning agent(s) to apolishing pad. Impeller assembly 84 serves to provide spraying aperturesfor the application of conditioning agent(s) and channels or sectionsfor waste material removal. In accordance with the present invention,the conditioning agent(s) may comprise a slurry of a specific chemistry(to assist in removing contaminants from the polishing pad via achemical reaction), ultra-pure water (UPW) or air to “flush”contaminants from the conditioning pad, any other suitable fluid orgaseous agent, or any combination thereof.

Referring to FIG. 7, a plurality of impeller blades 90-1 through 90-6are shown as attached to an upper holding member 92 of impeller assembly84. It is to be understood that this configuration is exemplary onlyand, in fact, an impeller arrangement of this embodiment of the presentinvention may include only a single impeller blade. An exemplaryimpeller blade 90-n is shown as including a plurality of apertures 94along its bottom surface 91, through which the conditioning agent(s)is/are introduced to the system. In the most general case, a singleaperture 94 may be formed on bottom surface 91, where a plurality ofsuch apertures 94 is considered to be preferred for most embodiments. Insystems that include a plurality of impeller blades, one or more of theblades may include these apertures 94. With respect to FIG. 7, impellerblade 90-n includes a channel system 93 formed within impeller blade90-n and terminating at each aperture 94. As discussed above,conditioning agent(s) is/are introduced through an inlet port 83 ofouter housing 82. The conditioning agent then passes through an openingin center member 97 of impeller assembly 84 and is then introduced toeach channel system 93, as shown in FIG. 7. The conditioning agent flowsalong channel 93 and exits impeller assembly 84 at each aperture 94, forexample, as a “spray” of liquid material. The conditioning agent willthen pass through apertures 96 in magnetic disk 86, and apertures 98 inconditioning disk 88 so as to be dispersed across the surface of thepolishing pad. FIG. 8 is a cross-sectional view of the inventiveimpeller assembly 80, illustrating in particular the interaction of thevarious components discussed above to provide for the application of aconditioning agent to a polishing pad. It is an advantage of the presentinvention that the use of a plurality of apertures 94 on at least oneimpeller blade 90-n, coupled with the rotational movement of impellerassembly 84 (as indicated by the arrows in FIG. 7), provides forimproved coverage of the conditioning agent on the polishing padsurface, thereby allowing for more contaminant to be removed and for theconditioning process to be more efficient. This rotational movement ofimpeller assembly 84 is controlled by an abrasive conditioning diskdrive motor 81, as shown. As will be discussed hereinbelow, a torquemeasurement instrument may be used in conjunction with drive motor 81 toanalyze the applied rotational torque and determine parameters such as,but not limited to, the thickness of the polishing pad (i.e., an agingmeasurement). In one embodiment of the present invention, thetemperature of the conditioning agent may be controlled as desired. Forexample, the temperature of a conditioning slurry may be controlled soas to control the rate of chemical reaction between the polishing padand the conditioning slurry. Alternatively, the temperature of theconditioning agent may be controlled to reduce the heat created by theconditioning process itself.

In accordance with one embodiment of the present invention, spentconditioning agent(s), polishing slurry, contaminants, debris, etc.(hereinafter referred to as “effluent”) may be removed using a vacuumprocess. A plurality of vacuum ports 102 are illustrated in FIG. 7 asformed around the inner periphery of outer housing 82. A vacuum coupling104 is formed on the outer surface of outer housing 82 and coupled to avacuum source (not shown). Housing 82 includes a vacuum channel 106within its walls that is coupled to vacuum ports 102 so that as a vacuumis applied at outer port 104, a vacuum will start to draw through ports102, and then through apertures 96 and 98 of magnetic disk 86 andconditioning disk 88, respectively. Advantageously, the use of theapertured disks 86 and 88 allows for a significant portion of theeffluent to be efficiently evacuated through the relatively large numberof aligned openings formed in the combination of disks 86, 88. In theparticular embodiment as shown in FIG. 7, a set of six vacuum regionsare formed, with impeller blades 90-1 through 90-6 serving as barriersbetween adjacent vacuum regions. FIG. 9 is a bottom, isometric view ofan exemplary conditioning system of the present invention, particularlyillustrating the formation of the different vacuum segments, where FIG.8 illustrates the path the effluent will traverse above magnetic disk86, through vacuum ports 102, into vacuum channel 106 and thereafterexiting through outer vacuum port 104.

In an alternative embodiment, as illustrated in FIG. 10, impellerassembly 84 may be configured to include at least one vacuum port 100formed on bottom surface 91 of at least one blade 90-n, where in thealternative a plurality of such vacuum ports are included on at leastone blade 90-n. In order to easily remove larger particles of debris andcontaminant, vacuum port 100 may have a larger opening than apertures 94formed on the same blade 90-n. Referring to FIG. 10, vacuum ports 100are illustrated as coupled to a vacuum channel 101 along the topinterior portion of impeller blade 90-n, such that the effluent from thepad surface may be pulled out through vacuum ports 100, pass throughchannel 101, and thereafter be directed to the same or similar outervacuum port 104 (as shown in FIG. 7). In accordance with the presentinvention, the rotation of impeller assembly 84, coupled with theapplication of a vacuum through a number of different vacuum ports 100,allows for a significant amount of effluent to be removed quickly andefficiently.

It is to be understood that there may be occasions where an impellerarrangement of the present invention is configured only to apply aconditioning agent to a polishing pad (i.e., does not include any vacuumports or vacuum evacuation system), or configured only to evacuateeffluent from the polishing pad surface through the inventive aperturedconditioning disk (using any other technique to apply conditioningagents to the polishing pad surface). In either instance, an impellerarrangement of the present invention is configured to include theappropriate apertures/vacuum ports to be used as discussed above.

Another advantage of the improved impeller arrangement 80 of the presentinvention is the use of a central locating key 110 for properly aligningmagnetic disk 86 and conditioning pad 88 (or only pad 88 in systemswithout a support disk) with impeller assembly 84. In the arrangement asillustrated in FIG. 7, a central locating key 110 is configured to fitthrough a central aperture 112 in conditioning disk 88 and then througha central aperture 114 in magnetic disk 86. Locating key 110 is properlydesigned such that the disks will be aligned with each other uponjoining. In the particular example as illustrated in FIG. 7, a hexagonalkey is used as the locating key, where the hexagonal shape will preventthe movement of conditioning disk 88 with respect to magnetic disk 86.The joined components are then attached to the underside of impellerassembly 84, where a central locking element 116 of impeller assembly 84functions to align the apertures 96, 98 of magnetic disk 86 andconditioning pad 88 with apertures 94 and/or vacuum ports 100 of eachimpeller blade 90-n. By virtue of the large number of apertures formedwithin magnetic disk 86 and conditioning disk 88, the ease of alignmentbetween the apertures of these components with apertures 94 and/orvacuum ports 100 is enhanced. Referring to FIG. 7, a pair of lockingpins 120, 122 of central locking element 116 extend through theassembled components and are then inserted in mating openings 124, 126formed in central locating key 110. A screw or other attachment meansmay be inserted through central opening 130 of central locating key 110to central locking element 116 to mechanically secure the arrangement.FIG. 9 also contains a view of this locking arrangement as seen from thebottom of the arrangement. Although a hexagonal locating shape isillustrated in FIG. 7, it is to be understood that other geometries maybe used in the formation of central locating key 110, for the purpose ofcreating a mechanical attachment, properly aligning the tooling of thesystem and providing for transfer of the drive/rotational force to theconditioning assembly. Moreover, the locking mechanical attachment hasbeen found to prevent misalignment of conditioning disk 88 with respectto gimbaled impeller assembly 84, thus maintaining an essentiallyparallel relationship that limits uneven polishing pad wear.

In one embodiment of the present invention, a pressurized source 128 iscoupled to impeller arrangement 80 and used to impart an impulsefunction to the streams of slurry/conditioning agent being applied tothe polishing pad. The use of a megasonic stream will advantageouslydislodge contaminants that have become embedded in the top surface,fibers and/or pores of the polishing pad being conditioned. The presenceof the vacuum then allows for these dislodged contaminants to be quicklyand efficiently removed from the surface of the polishing pad. Thereexist various arrangements that may be used to provide for the megasonicstreams, such as the use of a separate pressurizing element for eachimpeller blade. Referring to FIG. 7, a piezo-electric driver 99 may beincluded within impeller blade 90-n to provide sonic energy and excitethe flow of the conditioning agent. Alternatively, one pressurizingsource (such as element 128) may be used to impart an impulsepressurized force for the stream of conditioning agent(s) introducedthrough the inlet port.

FIG. 11 illustrates, in a bottom view, an alternative embodiment ofimpeller assembly 84 of the present invention. FIG. 12 is a cut-awayside view of this embodiment, taken along line 12-12 of FIG. 11. In thiscase, impeller blades 90 are replaced by a plurality of separateimpeller elements 160, each element being cylindrical in form (see FIG.12), including a central aperture 164 for dispensing the conditioningagent(s) surrounded by a cylindrical encasement 166. As with theembodiments described above, the precise location and size of eachimpeller element 160 is at the discretion of the system designer. In theembodiment of FIG. 11, the plurality of impeller elements 160 arearranged as a set of “spokes” 162. That is, separate sets of impellerelements 160 are disposed in linear fashion, extending outward fromcenter member 97, forming spokes 162-1 through 162-6. With particularreference to FIG. 12, a channel 168 may be formed within upper holdingmember 92 to provide a path for the conditioning agent(s) to flow and bedispensed through apertures 164 of impeller elements 160. Therefore,similar to the blade embodiment described above, this arrangement ofimpeller elements 160 forms a set of six separate segments that willallow for efficient application of the conditioning agent(s) and/orvacuum removal of the effluent. It is to be presumed that thearrangement of impeller elements 160 is controlled to the extent thatcentral apertures 164 will align with apertures 96 and 98 of magneticdisk 86 and conditioning disk 88, respectively.

FIG. 13 illustrates an alternative embodiment of impeller assembly 84that comprises a plurality of separate impeller elements 160 disposed ina more random pattern across the surface of upper holding member 92. Inthis case, a different channel configuration would be required to ensurethat each impeller element 160 desired to be used to dispenseconditioning agent(s) is in contact with a channel. In the particularembodiment of FIG. 13, a first set of impeller elements 160-V may bedisposed around the perimeter of upper holding member 92 and coupled toa vacuum channel (similar to channel 101 discussed in association withFIG. 10) to evacuate effluent from the surface of a polishing pad. Theremainder of the impeller elements, designated as 160-C, would then beused to dispense the conditioning agent(s).

It is to be understood that the various embodiments of the impellerassembly discussed hereinabove are exemplary only, and it is to beunderstood that various other arrangements for dispensing conditioningagent(s) and/or evacuating effluent are considered to fall within thespirit and scope of the present invention.

In comparison to prior art conditioning processes and systems, thearrangement of the present invention provides for the conditioning andassociated polishing processes to be considerably more efficient. Inparticular, the inventive arrangement uses significantly less materials(e.g., polishing slurry, cleaning/rinsing agents) to perform thepolishing and conditioning operations. Typical wafer polishing processesrequire the dispensing of anywhere from about 140-250 ml/minute ofpolishing slurry to provide stable polishing, since a portion of thereacted slurry remains in the sponge-like pores of the pad after eachrotation. Using the conditioning arrangement of the present invention,the pores of the polishing pad are thoroughly cleaned of reacted slurry,presenting the pad as a “fresh”, dry sponge for the introduction of thenext dispensing of polishing slurry. As a result of the absence ofreacted and “new” slurry within the pores of the polishing pad, lessslurry is required to perform the same amount of polishing. For example,a polishing flow on the order of 75-100 ml/min has been found acceptablefor systems formed in accordance with the present invention. It is to beunderstood that similar reductions in the amounts and flow rates ofvarious conditioning agents can also be expected.

The improvement of using a “recharged”, clean pad during each polishingoperation may also be analyzed in terms of the amount of materialactually removed during the polishing operation (defined as the removalrate and measured in Å/min). FIG. 14 contains a graph comparing theaverage thermal oxide removal rate for a conventional prior artconditioning system vs. the conditioning system of the presentinvention, the graph based on an extended polishing run utilizing a flowrate for the polishing slurry of 100 ml/min. As shown, the averageremoval rate for the prior art was about 1944 Å/min, compared to aremoval rate of 2183 Å/min for an arrangement formed in accordance withthe present invention. FIG. 15 contains a graph of the removal rate (inthis case, thermal oxide polishing), as a function of the vacuum levelapplied to the pad during the conditioning process. In this particularcase, a 5-7% increase in removal rate was found for a vacuum in therange of 6″-9″ Hg. Further, the consumption of conditioning agentsand/or rinsing water is also reduced, for the same reasons, particularlywith respect to the use of a vacuum to draw the effluent through theapertures. Other results, of course, could be possible in other systems.

As a result of the need to use less conditioning agent and/or rinseagent, and because the effluent is captured from the pad surface and notdiluted with other machine wastes, the amount of polished film material(for example, copper) present in the evacuated material is much moreconcentrated. Therefore, the waste material may preferably be segregatedand processed, allowing for a significant amount of the polished filmmaterial (i.e., copper) to be reclaimed. Additionally, a chemicalanalyzer may be included as part of the waste removal system and used toprovide in situ determination of the end point of the polishing process.That is, by monitoring the concentration of various components of filmmaterial present in the waste stream, the point where a wafer substrateis reached, or where a bulk film layer has been completely removed, canbe determined.

Yet another feature of impeller arrangement 80 of the present inventionis the possibility of modifying sealing surface 131 of outer chamber 82to provide for a dynamic seal between the conditioning apparatus and thepolishing pad surface. In this case, outer chamber 82 is attached as a“floating” member to an end effector arm supporting the conditioningapparatus (such as end effector arm 16 of FIG. 1). In one embodiment the“floating” outer chamber may include a solid sealing surface,particularly well-suited for use with grooved polishing pads. When usedwith perforated polishing pads, this sealing surface may be textured.Advantageously, the use of a vacuum system to remove spent conditioningagent and contaminants allows for a vacuum seal to be created betweenouter chamber 82 and the polishing pad. This vacuum force, in theembodiment where it is applied in the vacuum regions between adjacentimpeller blades, maintains an essentially co-planar interface betweenconditioning disk 88 and the surface of the polishing pad, whereimproved co-planarity will allow for improved uniformity of the abrasivepressure and orientation of conditioning disk 88 (e.g., flatness/diamondfurrow density/surface profile) and improved uniformity with respect toremoval of contaminants from the polishing pad. Moreover, the use ofvacuum seal between outer chamber 82 and the polishing pad will reducethe amount of “plowing” that occurs in conventional systems when thegimbaled conditioning apparatus rotates or tilts slightly toward theleading edge in response to sliding contact/friction with the surface ofthe polishing pad. FIGS. 16(a) and (b) contain illustrations of thecontact pressure between a conditioning disk and polishing pad surface,where FIG. 16(a) is associated with a prior art conditioning system andFIG. 16(b) is associated with a conditioning system formed in accordancewith the present invention. These pictures were obtained using a Tekscanforce measurement array. A conventional conditioner was mounted on anIPEC 372M CMP tool, and contact force measurements were taken overincreasing loads. FIG. 16(a) clearly illustrates a localized highpressure zone A (i.e., “plowing”) that is associated with the leadingradius of the conditioner. The vacuum enhanced conditioning system ofthe present invention was similarly tested, with a constant mechanicaldownforce, and increasing vacuum “loads”. The resultant force plot ofFIG. 16(b) clearly illustrates uniform loads (denoted as area “B”) overthe entire abrasive surface.

Additionally, the controlled application of a bi-directional force(i.e., upward force through the effector arm on the conditioning systemand downward vacuum applied force), in accordance with the presentinvention, allows for better control of the resultant force (thisresultant force being maintained, for example, between 0 and 50 pounds).In particular, by dynamically controlling the “negative pressure” of thevacuum force, the actual vacuum can be modified as desired to providefor more efficient contaminant removal, as noted above, without creatingexcessive or additional force on the abrasive that would then lead toundesirable higher polishing pad removal rates.

In general, the use and control of the bi-directional force allows forclosed loop control of the polishing pad removal rate via parameterssuch as torque, speed, displacement, force, “z” and “x/y” position, etc.The conditioning arm may further include, as part of this closed loopcontrol system, multi-axis force instrumentation that provides for highresolution and dynamic resultant downforce and torsional momentmeasurements, all used as feedback information to the closed loopsystem. FIG. 17 contains a simplified diagram illustrating the use ofabrasive torque instrumentation 200, used to measure the rotationaltorque of abrasive conditioning disk drive motor 81 as conditioningsystem 80 is pivoted across the platen radius of a CMP tool, wherechanges in rotational torque can be directly correlated to changes inpolishing pad thickness. The abrasive torque measurement andconditioning pad wear measurement systems may be included in the closedloop system to monitor the “lifetime” of the polishing pad and providedata regarding end of life detection. Typically, polishing pad life isspecified/controlled in terms of number of wafers processed. This isoften a conservative approximation and does not account for variationssuch as, for example, break-in, interruptions, abrasive sharpness, waferfilm variations, etc. By measuring the actual surface profile andremaining thickness of the polishing pad in situ, a much more accurateend of life control mechanism is obtained. In particular, the torque ofthe abrasive conditioning disk drive motor 81 may be measured andanalyzed with respect to vertical displacement/abrasive wear, resultantdownforce (i.e., combination of vacuum-generated force andmechanically-supplied force), rotational speed, and pad sweep position(radius) to determine the Preston constant (K). This measurement ofrotational torque on abrasive drive motor 81 is a unique distinction incomparison to the prior art, where the torque measurements are made atthe pivot arm (the pivot arm measurements considered as being a lessaccurate indication of the actual attributes of the abrasiveconditioning disk). This analysis of the motor torque then yields theability to control downforces and speeds in different radial positionsacross the polishing pad so as to better manage removal rate and overallpolishing pad surface planarity.

The method of providing operation specific slurries 50 of the presentinvention is shown in the block diagram of FIG. 6. Cleaning thepolishing pad 51 in process is comprised of at least five operations runin parallel, sequentially or any combination. This operation can be runin-situ or ex-situ, and can support dynamic in-process pH adjustments tocontrol removal rate and/or endpoint selectivity. The polishing pad 12is subjected to a vibratory motion 52 to remove processing debris ofloose slurry, fluids, and gasses 52A. The static layer that may remainis destabilized 53 with vacuum, water and other chemicals 53A. Thepolishing pad surface, pores, and grooves 54 are then cleaned withvacuum, water and chemicals 54A. A further step involves neutralizingthe slurry 55 residue on the pad surface with water and other chemicals55A. The final step is flushing 56 to remove cleansing fluids and anyremaining debris 56A. With the conditioning apparatus thoroughlycleaned, other operation specific slurries 57A, 57B, and 57C may beintroduced to the process via slurry feed system or at 57 to theconditioning apparatus 10.

1. An apparatus for conditioning a polishing pad used in achemical-mechanical polishing (CMP) process, the apparatus comprising anabrasive conditioning disk including a plurality of apertures formedtherethrough; an inlet port for introducing fluid and/or gaseousconditioning agent(s) into the apparatus, through the abrasiveconditioning disk plurality of apertures, and onto a polishing pad; anda vacuum supply coupled to the polishing pad through the abrasiveconditioning disk apertures, wherein upon activation of an exteriorvacuum source, effluent from the conditioning process will be drawnthrough said abrasive conditioning disk apertures and evacuated from theapparatus.
 2. The apparatus as defined in claim 1 wherein the vacuumsupply comprises an outer vacuum chamber disposed to surround theabrasive conditioning disk, the outer vacuum chamber comprising a vacuumport formed on the exterior surface thereof and a vacuum channel formedwithin the interior thereof; and at least one vacuum port formed withinthe inner periphery of said outer vacuum chamber, the at least onevacuum port coupled through the vacuum channel to the exterior surfacevacuum port such that upon activation of an exterior vacuum source,effluent from the conditioning process will be drawn through theconditioning disk apertures, the at least one vacuum port and the vacuumchannel, exiting the apparatus through the exterior vacuum port.
 3. Theapparatus as defined in claim 2 wherein the at least one vacuum portcomprises a plurality of vacuum ports formed around the inner peripheryof the outer vacuum chamber.
 4. The apparatus as defined in claim 2wherein the outer vacuum chamber includes a bottom seal surface forforming a vacuum seal with the polishing pad surface.
 5. The apparatusas defined in claim 2 wherein the bottom seal surface comprises a solidunit.
 6. The apparatus as defined in claim 2 wherein the bottom sealsurface comprises a textured unit.
 7. The apparatus as defined in claim2 wherein the outer vacuum chamber is coupled to the impeller assemblyby a non-fixed attachment so as to allow for the chamber to “float” overundulations in the surface of a polishing pad.
 8. Apparatus forconditioning a polishing pad used in a chemical-mechanical polishing(CMP) process, the apparatus comprising an abrasive conditioning diskincluding a plurality of apertures formed therethrough; an inlet portfor introducing fluid and/or gaseous conditioning agent(s) into theapparatus, through the abrasive conditioning disk plurality of aperturesand onto a polishing pad; an impeller assembly disposed between theabrasive conditioning disk and the inlet port, the impeller assemblyincluding at least one impeller element having at least one vacuumaperture for removing effluent from a polishing pad, the effluentpassing through said plurality of apertures formed through saidconditioning disk and into the at least one vacuum aperture; and anouter vacuum chamber disposed to surround the impeller assembly and theabrasive conditioning disk, the outer vacuum chamber comprising a vacuumport formed on the exterior surface thereof; a vacuum channel formedwithin the interior thereof; and at least one vacuum exit port coupledto said at least one impeller element vacuum aperture such that uponactivation of an exterior vacuum source, effluent from the conditioningprocess will be drawn through the conditioning disk apertures and the atleast one vacuum aperture, exiting the apparatus through the exteriorvacuum port.
 9. The apparatus as defined in claim 8 wherein the at leastone vacuum aperture comprises a plurality of vacuum apertures formedalong the bottom surface of the at least one impeller element.
 10. Theapparatus as defined in claim 8 wherein the at least impeller elementcomprises a cylindrical member including a central vacuum aperture andsurrounding encasement.
 11. The apparatus as defined in claim 10 whereinthe at least one cylindrical member impeller element comprises aplurality of cylindrical member elements.
 12. The apparatus as definedin claim 8 wherein the at least one impeller element comprises animpeller blade, said at least one impeller blade disposed outward fromthe center of the impeller assembly and extending perpendicularly abovethe conditioning disk, said at least one impeller blade comprising aninterior channel formed along at least a portion thereof, coupled at afirst end to a vacuum exit port and terminating through at least onevacuum aperture formed in the bottom surface of said at least oneimpeller blade.
 13. The apparatus as defined in claim 12 wherein the atleast one impeller blade comprises a plurality of impeller blades,disposed in a radial pattern and extending outward from the center ofthe impeller assembly, with a separation between adjacent impellerblades.
 14. The apparatus as defined in claim 13 wherein at least twoimpeller blades of the plurality of impeller blades include at least onevacuum aperture for evacuation of the effluent.
 15. The apparatus asdefined in claim 8 wherein the at least one vacuum aperture comprises aplurality of vacuum apertures for evacuating effluent.
 16. The apparatusas defined in claim 8 wherein the apparatus further comprises a supportdisk disposed in between the abrasive conditioning disk and the impellerassembly, the support disk comprising a plurality of apertures thatalign with the abrasive conditioning disk plurality of apertures. 17.The apparatus as defined in claim 16 wherein the support disk comprisesa magnetic material for providing a fixed attachment of the support diskto the abrasive conditioning disk.
 18. The apparatus as defined in claim16 wherein the apparatus further comprises a central locating key forcoupling with the support disk and the abrasive conditioning disk, saidsupport disk and said abrasive conditioning disk both including acentral locating key opening; and the impeller assembly including acentral locking element, the central locking element for mating with thecentral locating key through the central locating key openings of saidsupport disk and said abrasive conditioning disk, so as to transferrotational energy from said impeller assembly to said conditioning disk.19. The apparatus as defined in claim 18 wherein the central locatingkey, central locking element, and the central locating openings exhibita hexagonal form.
 20. The apparatus as defined in claim 8 wherein theapparatus further comprises a central locating key for coupling with theabrasive conditioning disk, the abrasive conditioning disk including acentral locating key opening; and the impeller assembly including acentral locking element, the central locking element for mating with thecentral locating key through the central locating key opening of saidconditioning disk, so as to transfer rotational energy from saidimpeller assembly to said conditioning disk.
 21. A method ofconditioning a polishing pad used in a chemical-mechanical polishing(CMP) process, the method comprising the steps of: introducingconditioning agent(s) to the process through at least one apertureformed in at least one impeller element of an impeller assembly;allowing the introduced conditioning agent(s) to flow through aplurality of apertures formed through an abrasive conditioning disk; androtating the impeller assembly with respect to a polishing pad todistribute conditioning agent(s) along a surface portion of a polishingpad.
 22. The method as defined in claim 21 wherein the method furthercomprises the step of: imparting pressurized energy to the conditioningagent(s) prior to allowing the conditioning agent(s) to reach thepolishing pad surface.
 23. The method as defined in claim 22 wherein theimparting step comprises the steps of: coupling a piezo-electricmegasonic energy source to the at least one impeller element; andactivating said piezo-electric megasonic energy source to impartmegasonic energy to said conditioning agent(s).
 24. The method asdefined in claim 21 wherein the temperature of the conditioning agent iscontrolled in association with other process parameters.
 25. The methodas defined in claim 21 wherein the method further comprises the stepsof: measuring the rotational torque of the abrasive conditioning disk;analyzing the measured torque value with respect to predeterminedprocess parameters to assess the polishing pad removal rate andpolishing pad surface planarity; and controlling the conditioning diskdownforce and speed in different radial positions across a polishing padwith respect to the analyzed values of the polishing pad removal rateand polishing pad surface planarity.
 26. A method of conditioning apolishing pad used in a chemical-mechanical polishing (CMP) process, themethod comprising the steps of: introducing conditioning agent(s) to theprocess through a plurality of apertures formed through an abrasiveconditioning disk; using an outer vacuum chamber surrounding theabrasive conditioning disk, the outer vacuum chamber including at leastone vacuum port disposed to evacuate effluent from the polishing pad;and removing conditioning agent(s) and contaminants from the polishingpad and through said plurality of apertures of the conditioning disk aseffluents through said at least one vacuum port formed in said outervacuum chamber.
 27. The method as defined in claim 26 wherein the methodfurther comprises the step of: capturing the removed effluent.
 28. Themethod as defined in claim 27 wherein the method further comprises thesteps of: filtering the captured effluent to separate out theconditioning agent(s); and re-introducing the separated conditioningagent to the conditioning process.
 29. The method as defined in claim 27wherein the method further comprises the steps of segregating thecaptured effluent; and reclamating selected captured effluent.
 30. Themethod as defined in claim 27 wherein the method further comprises thestep of: performing chemical analysis on said captured effluent todetermine the end point of the on-going polishing process.
 31. A methodof conditioning a polishing pad used in a chemical-mechanical polishing(CMP) process using conditioning agent(s), the method comprising thesteps of: providing an outer vacuum chamber to surround an abrasive,apertured conditioning disk, said outer vacuum chamber including atleast one vacuum port to evacuate effluent from the polishing pad; andremoving conditioning agent(s) and contaminants from said polishing padthrough the apertured conditioning disk as effluents through said atleast one vacuum port formed in said outer vacuum chamber.
 32. Themethod as defined in claim 31 wherein the method further comprises thestep of: capturing the evacuated effluent.
 33. The method as defined inclaim 32, wherein the method further comprises the steps of: filteringthe captured effluent to separate out the conditioning agent(s); andre-introducing the separated conditioning agent(s) to the conditioningprocess.
 34. The method as defined in claim 32 wherein the methodfurther comprises the step of: performing chemical analysis on saidcaptured effluent to determine the end point of the on-going polishingprocess.
 35. The method as defined in claim 31 wherein the methodfurther comprises the step of: adjusting the temperature of theconditioning agent(s) to control the chemically-induced reaction rate ofmaterial on the polishing pad.
 36. A method for manufacturing asemiconductor wafer, the method comprising the steps of: placing asemiconductor wafer surface in contact with a polishing pad;conditioning the polishing pad by using the steps of: introducingconditioning agent(s) to the process through at least one apertureformed in at least one impeller element of an impeller assembly;allowing the introduced conditioning agent(s) to flow through aplurality of apertures formed through an abrasive conditioning disk; androtating the impeller assembly with respect to a polishing pad todistribute conditioning agent(s) along a surface portion of a polishingpad; and polishing the semiconductor wafer surface with the cleanedpolishing pad.